function saveCanvas() {
  saveCanvasButton.download = "image.png";
  saveCanvasButton.href = canvas.toDataURL("image/png").replace("image/png", "image/octet-stream");
}

function goFullScreen() {
  if (canvas.requestFullScreen)
    canvas.requestFullScreen();
  else if (canvas.webkitRequestFullScreen)
    canvas.webkitRequestFullScreen();
  else if (canvas.mozRequestFullScreen)
    canvas.mozRequestFullScreen();
}